Fixes invalid encoding of VPERMQ and VPERMPD that use
negative immediate argument.

Fixes #25418
Updates #25420

Change-Id: Idd8180c4c632a76b76f3a68efd5f930d94431994
Reviewed-on: https://go-review.googlesource.com/113615
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Ilya Tocar <ilya.tocar@intel.com>